The present invention generally relates to the field of semiconductor devices, and more particularly relates to passivation of surfaces of semiconductor devices.
In modern semiconductor electronics technology, InxGa(1−x)As where 0<x<1 (indium gallium arsenide, InGaAs) is a III-V compound semiconductor material that can be used in semiconductor structures and devices for high performance (e.g., very high speed, low noise, and very low power consumption) applications such as in electronics, wireless communications, and optoelectronics. For example, high-electron-mobility-transistor (HEMT) devices using InGaAs channels are one of the fastest types of transistors. Electron mobility and hole mobility are key parameters for design and performance of electronic devices. InGaAs devices at the interface surface of the InGaAs layer material can have very high value of electron mobility and a very large ratio of electron to hole mobility. The mobility is proportional to the carrier conductivity. As mobility increases, so does the current-carrying capacity of transistors. A higher mobility shortens the response time of the semiconductor devices and reduces series resistance, and accordingly improves semiconductor device efficiency and reduces noise and power consumption.
However, InGaAs material has some limitations in terms of a high density of surface defects at an interface surface of an InGaAs layer that typically limits the device performance. For example, when a dielectric material having a dielectric constant that is greater than silicon dioxide (k greater than 4.0) is deposited on a InGaAs semiconductor material that has an unpassivated surface, the interface between the high-k dielectric and the InGaAs semiconductor material is typically poor, resulting in a high interface defect density (on the order of about 1013 cm−2 eV−1 or greater). Surface passivation of an interface surface of indium gallium arsenide (InGaAs) layer material is a critical process to fabricate high performance microelectronic devices. Passivation of an interface surface of indium gallium arsenide (InGaAs) layer material typically involves creation of a layer of material that is applied as a microcoating typically created by chemical reaction with the base InGaAs material at the interface surface.
Sulfurization of the InGaAs material surface is a promising passivation option in terms of passivation of the interface surface of the InGaAs layer material to reduce the surface defect density. A conventional process for passivation of an interface surface of indium gallium arsenide (InGaAs) layer material involves applying ammonium sulfide ((NH4)2S) chemical solution in a wet chemical based treatment. This wet chemical treatment process has undesirable attributes for a semiconductor fabrication process, including: 1) the wet treatment decomposes at room temperature, 2) it releases very offensive smell, 3) the chemicals used are very toxic, and 4) a reaction temperature of the applied ammonium sulfide ((NH4)2S) chemical solution normally cannot exceed approximately 100 degrees Celsius (boiling temperature).